diff --git a/lib/backend.py b/lib/backend.py
index bb5bfe04812f3a53989e2f85aaea1b72262f49dc..4415223d2f2cae291bdc5774240381bf3310ce65 100644
--- a/lib/backend.py
+++ b/lib/backend.py
@@ -942,10 +942,10 @@ def _OSSearch(name, search_path=None):
   if search_path is None:
     search_path = constants.OS_SEARCH_PATH
 
-  for dir in search_path:
-    t_os_dir = os.path.sep.join([dir, name])
+  for dir_name in search_path:
+    t_os_dir = os.path.sep.join([dir_name, name])
     if os.path.isdir(t_os_dir):
-        return dir
+      return dir_name
 
   return None
 
@@ -1006,16 +1006,17 @@ def DiagnoseOS(top_dirs=None):
     top_dirs = constants.OS_SEARCH_PATH
 
   result = []
-  for dir in top_dirs:
-    if os.path.isdir(dir):
+  for dir_name in top_dirs:
+    if os.path.isdir(dir_name):
       try:
-        f_names = utils.ListVisibleFiles(dir)
+        f_names = utils.ListVisibleFiles(dir_name)
       except EnvironmentError, err:
-        logger.Error("Can't list the OS directory %s: %s" % (dir,str(err)))
+        logger.Error("Can't list the OS directory %s: %s" %
+                     (dir_name, str(err)))
         break
       for name in f_names:
         try:
-          os_inst = OSFromDisk(name, base_dir=dir)
+          os_inst = OSFromDisk(name, base_dir=dir_name)
           result.append(os_inst)
         except errors.InvalidOS, err:
           result.append(objects.OS.FromInvalidOS(err))
diff --git a/lib/bdev.py b/lib/bdev.py
index a2d7e4f30c1506fcca378461f67aa7989410a2e3..bfa333b7b055cf4fad1595471c7c6da9e0dd8600 100644
--- a/lib/bdev.py
+++ b/lib/bdev.py
@@ -2146,7 +2146,7 @@ class DRBD8(BaseDRBD):
     self.unique_id = new_uid
     if not self._AssembleNet(self.minor, self.unique_id, "C"):
       logger.Error("Can't attach to new peer!")
-      if self.old_id is not None:
+      if old_id is not None:
         self._AssembleNet(self.minor, old_id, "C")
       self.unique_id = old_id
       raise errors.BlockDeviceError("Can't attach to new peer")
diff --git a/lib/cli.py b/lib/cli.py
index 780e002e433c86674e28cff5155ad90113de148d..2f3dbf7214eab044284e4ddfb9104f58329e5919 100644
--- a/lib/cli.py
+++ b/lib/cli.py
@@ -195,6 +195,9 @@ ARGS_ANY = ARGS_ATLEAST(0)
 
 
 def check_unit(option, opt, value):
+  """OptParsers custom converter for units.
+
+  """
   try:
     return utils.ParseUnit(value)
   except errors.UnitParseError, err:
@@ -202,6 +205,9 @@ def check_unit(option, opt, value):
 
 
 class CliOption(Option):
+  """Custom option class for optparse.
+
+  """
   TYPES = Option.TYPES + ("unit",)
   TYPE_CHECKER = copy.copy(Option.TYPE_CHECKER)
   TYPE_CHECKER["unit"] = check_unit
diff --git a/lib/cmdlib.py b/lib/cmdlib.py
index cb403383e80591bd9a5aeab3f0d09a1735a41a5b..6bd0ed03e675f21887ea0c26396d319efc73d330 100644
--- a/lib/cmdlib.py
+++ b/lib/cmdlib.py
@@ -26,7 +26,6 @@
 import os
 import os.path
 import sha
-import socket
 import time
 import tempfile
 import re
@@ -856,7 +855,6 @@ class LUVerifyCluster(NoHooksLU):
     feedback_fn("* Verifying global settings")
     self.cfg.VerifyConfig()
 
-    master = self.sstore.GetMasterNode()
     vg_name = self.cfg.GetVGName()
     nodelist = utils.NiceSort(self.cfg.GetNodeList())
     instancelist = utils.NiceSort(self.cfg.GetInstanceList())
diff --git a/lib/utils.py b/lib/utils.py
index f22537917efa99dcfaff498e4b719e0c1cf1efc7..56c0bf33869bd0ab4bf7b26131eb59c536651192 100644
--- a/lib/utils.py
+++ b/lib/utils.py
@@ -752,11 +752,11 @@ def CreateBackup(file_name):
                                 file_name)
 
   prefix = '%s.backup-%d.' % (os.path.basename(file_name), int(time.time()))
-  dir = os.path.dirname(file_name)
+  dir_name = os.path.dirname(file_name)
 
   fsrc = open(file_name, 'rb')
   try:
-    (fd, backup_name) = tempfile.mkstemp(prefix=prefix, dir=dir)
+    (fd, backup_name) = tempfile.mkstemp(prefix=prefix, dir=dir_name)
     fdst = os.fdopen(fd, 'wb')
     try:
       shutil.copyfileobj(fsrc, fdst)